Shrink or expand the header. Are you sure 21 bitcoin computer mining want to do this?
I have a crappy computer with an old grapics card and i’m thinking of building a dedicated GPU miner. How would you build a computer that is only to be used for mining bitcoins and nothing else? RAM and disk and off we go? Advertised sites are not endorsed by the Bitcoin Forum. They may be unsafe, untrustworthy, or illegal in your jurisdiction. How much are you willing to spend? You should look into pooled mining.
The best way to obtain bitcoins, in my opinion, is to buy them. Radeon card with high ratios. I’m unsure of the effects of mining with 2 cheap Radeon’s non crossfire versus 1 fancy Radeon by itself. It may be mostly additive. GFX takes MAJOR priority however.
More cores are better than faster cores. An AMD X6 or a newfangled intel i7 are ideal for maximum cores, but get expensive. GPU miner programs have minimal CPU impact. This is just to have a responsive overall system. Doesn’t need to be super fast or even big. Has the OS and your miners. A necessity since you’ll likely be overclocking whatever you use.
If price isn’t an issue, get an aftermarket CPU cooler or water cooler. Even if you don’t mess with CPU OC’s, GPU OC’ing is quick and easy and generates a lot of heat. 1200 cases are loved by everyone, are inexpensive, and are regarded as among the best air cooling towers you can get. Probably with some decent wattage headroom for upgrades down the line as the hashing difficulty factor increases. Make sure it accepts PCIe 2.